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block: Guard against NULL bs->drv

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We currently do not guard everywhere against a NULL bs->drv where we
should be doing so.  Most of the places fixed here just do not care
about that case at all.

Some care implicitly, e.g. through a prior function call to
bdrv_getlength() which would always fail for an ejected BDS.  Add an
assert there to make it more obvious.

Other places seem to care, but do so insufficiently: Freeing clusters in
a qcow2 image is an error-free operation, but it may leave the image in
an unusable state anyway.  Giving qcow2_free_clusters() an error code is
not really viable, it is much easier to note that bs->drv may be NULL
even after a successful driver call.  This concerns bdrv_co_flush(), and
the way the check is added to bdrv_co_pdiscard() (in every iteration
instead of only once).

Finally, some places employ at least an assert(bs->drv); somewhere, that
may be reasonable (such as in the reopen code), but in
bdrv_has_zero_init(), it is definitely not.  Returning 0 there in case
of an ejected BDS saves us much headache instead.

Reported-by: R. Nageswara Sastry <nasastry@in.ibm.com>
Buglink: https://bugs.launchpad.net/qemu/+bug/1728660
Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20171110203111.7666-4-mreitz@redhat.com
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Max Reitz 2017-11-10 21:31:09 +01:00
parent 93bbaf03ff
commit d470ad42ac
7 changed files with 130 additions and 3 deletions
Download patch file Download diff file Expand all files Collapse all files

36
block/io.c
View file

@ -853,6 +853,10 @@ static int coroutine_fn bdrv_driver_preadv(BlockDriverState *bs,
assert(!(flags & ~BDRV_REQ_MASK));
if (!drv) {
return -ENOMEDIUM;
}
if (drv->bdrv_co_preadv) {
return drv->bdrv_co_preadv(bs, offset, bytes, qiov, flags);
}
@ -894,6 +898,10 @@ static int coroutine_fn bdrv_driver_pwritev(BlockDriverState *bs,
assert(!(flags & ~BDRV_REQ_MASK));
if (!drv) {
return -ENOMEDIUM;
}
if (drv->bdrv_co_pwritev) {
ret = drv->bdrv_co_pwritev(bs, offset, bytes, qiov,
flags & bs->supported_write_flags);
@ -945,6 +953,10 @@ bdrv_driver_pwritev_compressed(BlockDriverState *bs, uint64_t offset,
{
BlockDriver *drv = bs->drv;
if (!drv) {
return -ENOMEDIUM;
}
if (!drv->bdrv_co_pwritev_compressed) {
return -ENOTSUP;
}
@ -975,6 +987,10 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child,
BDRV_REQUEST_MAX_BYTES);
unsigned int progress = 0;
if (!drv) {
return -ENOMEDIUM;
}
/* FIXME We cannot require callers to have write permissions when all they
* are doing is a read request. If we did things right, write permissions
* would be obtained anyway, but internally by the copy-on-read code. As
@ -1291,6 +1307,10 @@ static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs,
bs->bl.request_alignment);
int max_transfer = MIN_NON_ZERO(bs->bl.max_transfer, MAX_BOUNCE_BUFFER);
if (!drv) {
return -ENOMEDIUM;
}
assert(alignment % bs->bl.request_alignment == 0);
head = offset % alignment;
tail = (offset + bytes) % alignment;
@ -1397,6 +1417,10 @@ static int coroutine_fn bdrv_aligned_pwritev(BdrvChild *child,
uint64_t bytes_remaining = bytes;
int max_transfer;
if (!drv) {
return -ENOMEDIUM;
}
if (bdrv_has_readonly_bitmaps(bs)) {
return -EPERM;
}
@ -1863,6 +1887,8 @@ static int coroutine_fn bdrv_co_block_status(BlockDriverState *bs,
bytes = n;
}
/* Must be non-NULL or bdrv_getlength() would have failed */
assert(bs->drv);
if (!bs->drv->bdrv_co_get_block_status) {
*pnum = bytes;
ret = BDRV_BLOCK_DATA | BDRV_BLOCK_ALLOCATED;
@ -2373,6 +2399,12 @@ int coroutine_fn bdrv_co_flush(BlockDriverState *bs)
}
BLKDBG_EVENT(bs->file, BLKDBG_FLUSH_TO_DISK);
if (!bs->drv) {
/* bs->drv->bdrv_co_flush() might have ejected the BDS
* (even in case of apparent success) */
ret = -ENOMEDIUM;
goto out;
}
if (bs->drv->bdrv_co_flush_to_disk) {
ret = bs->drv->bdrv_co_flush_to_disk(bs);
} else if (bs->drv->bdrv_aio_flush) {
@ -2542,6 +2574,10 @@ int coroutine_fn bdrv_co_pdiscard(BlockDriverState *bs, int64_t offset,
num = max_pdiscard;
}
if (!bs->drv) {
ret = -ENOMEDIUM;
goto out;
}
if (bs->drv->bdrv_co_pdiscard) {
ret = bs->drv->bdrv_co_pdiscard(bs, offset, num);
} else {